[GDTRFB]

I just got a new bike with SRAM Red 2012. Aside from a very short ride the day I got the bike, I have only been able to use it on a trainer (too much snow).
On the trainer, the rear shifting is a little sluggish on the small cogs. I can't shift to the 11 while using the 34 up front. I also get chain rub on the FD with the 34/28 combo.
But when I have the bike on the repair stand, not under load, shifting is flawless, no hesitation, no rubbing.

Does anyone have any ideas as to what the problem could be or how to fix it?

 

[FTR]

Dont ride in the 34/11.
You are not meant to cross chain like that.
My 2 SRAM bikes are the same.

 

[GDTRFB]

Dont ride in the 34/11.
You are not meant to cross chain like that.
My 2 SRAM bikes are the same.

Do you have 2012 Red? There is no trim feature on the 2012 Red.
According to the video on SRAM's website, all 20 combos can be used. I don't plan on using the 34/11, but I will use the 34/28.
I can use all 20 combos (using the FD trim only for a couple of gears) with my 2011 Force.

 

[FTR]

2011 Red.
I can get to the 39/11 but it is not happy.

 

[GDTRFB]

2011 Red.
I can get to the 39/11 but it is not happy.

I can go to the 34/11 (on my 2011 Force) without much trouble, but I don't use that combo.

I just had that bike completely overhauled, new bearings, cables etc., and now rear shifting while on the small front ring hesitates a little, even to the point of "skipping" without shifting, when going up to a larger cog. Any thoughts on this?

 

[FTR]

Could be many things including a simple adjustment of the cable tension.

 

[FBinNY]

It isn't rare for bikes to shift slightly differently on a stand than in the real world. That's why many mechanics like to confirm their adjustments with a road test.

Since the bike is new, and it's getting warmer very soon, I'd wait and see how it shifts on the road, since that's what really counts. Also this will allow the shop mechanic to confirm the issues you report with his own road test.

However, no adjustment will ever give you an FD which can trim rub free across the entire width of the cassette. Make sure it's trimmed to be rub free on the gears you actually use, ie. inner with the inner half of the cassette, and outer with the outer half of the cassette (either with mid cassette).

 

[locobaylor]

possible cable stretch and/or limit screws needing to be adjusted; that's my guess.

 

[TrojanHorse]

I would also check the cable routing on your RD - if you don't get that in just right you can experience some iffy shifting (I have a force RD, not red, so it may be different, but there is definitely a right way and a wrong way to connect the cable to the RD)

Adjust your FD to eliminate chain rub in your 34/28 - as FB pointed out, make sure it works in the gears you use. I don't know why you'd ever use 34/11 so ignore that one.

Good luck - my new yaw FD and rings are arriving next week, can't wait to try them out.

 

[looigi]

I have old Red and new Red. Probably an adjustment issue. I never use the trim position on the old Red. FWIW, a little rubbing isn't all bad as it alerts you to being cross chained, which isn't that heinous, but something to be aware of and correct when and if convenient.

 

[GDTRFB]

Adjust your FD to eliminate chain rub in your 34/28 - as FB pointed out, make sure it works in the gears you use. I don't know why you'd ever use 34/11 so ignore that one.

Good luck - my new yaw FD and rings are arriving next week, can't wait to try them out.

I'd never use the 34/11, but I'd only worry that if that combo doesn't work, that would be an indication of something being out of adjustment.